Because electronic cigarettes deliver nicotine without burning tobacco, they may offer a valuable alternative for smokers who cannot break their nicotine addiction. However, little is known about electronic cigarette emissions or the health problems they produce. Our long-term objectives are to understand how electronic cigarettes affect human health and to contribute to the scientific foundation that will be used to establish rational policies for regulating the manufacture, advertisement, and sale of electronic cigarettes. Our Preliminary Data demonstrate high concentrations of metals and metal nanoparticles in aerosol from a leading brand of electronic cigarette. The goal of the proposed research is to identify and quantify the metal content of electronic cigarette aerosols from a broad spectrum of products and designs, to examine the cytoxicity and genotoxicity of aerosols with metal content, and to examine biomarkers of metal exposure and effect in human electronic cigarette users. In our first Specific Aim, we will identify and quantify metals in electronic cigarettes from various brands and styles and determine how metal concentrations correlate with electronic cigarette design. Metal quantification will be done using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Characterization of particle structure and size will be done using scanning and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (EDS) to identify elements. Metal concentrations in aerosol will be examined as a function of puffing topology. In the second Specific Aim, we will determine if aerosols with metals produce cytotoxic and genotoxic effects in human cells using the MTT and comet assays, in combination with a novel liver cell metabolizing assay. Human embryonic stem cells will be used to model an early stage of prenatal development and three dimensional human bronchial/epithelial tissue exposed at an air-liquid interface will be used to model human lung exposure. In Aims 1 and 2, metals in electronic cigarettes will be compared to metals in three popular brands of combustible cigarettes. In Aim #3, we will use metal biomarkers to quantify metal exposure and effect in humans who use electronic cigarettes, determine if metal uptake by cells includes nanoparticles, and determine whether metals migrate to the bloodstream and are excreted in the urine. Our project will generate new data on: (1) the metal content of electronic cigarette aerosols across a broad spectrum of evolving products, (2) the cyto/genotoxicity of the metals in electronic cigarette aerosols, (3) the sensitivity of embryonic and differentiated adult lung cells to electronic cigarette aerosol metals, and (4) the absorption, excretion, and the biological effects of metals in human electronic cigarette users. These data, the first of their kind, will contribute to a foundation of science upon which the FDA can develop regulatory policies to protect consumers' health and minimize future public health problems.